Scientists found a new species hiding in a museum drawer for more than a century; the Ecuadorian frog had been mistaken for another species |

PC: Long overdue: a new, widespread, species of Pristimantis (Anura, Strabomantidae) from the Chocó region and the synonymy of Pristimantis subsigillatus​

For more than a century, a frog living across the forests of western Ecuador and southern Colombia carried the wrong scientific name. It was not hidden in some unexplored corner of the rainforest, either. The animal was relatively common; its distinctive night-time call made it easy to detect, and specimens had already been collected and preserved. The problem lay in how those specimens had been identified. The mystery eventually led Ecuadorian biologist Santiago Ron to the Natural History Museum in London, where 19th-century type specimens provided the clue needed to untangle the old classification. By comparing the historic material with living frogs, researchers found that populations long labelled Pristimantis subsigillatus actually represented a different species. That species has now been formally described as Pristimantis milpe. Its discovery shows how a scientific name can remain attached to the wrong animal for generations, and how an old museum specimen can finally set the record straight.

How a museum specimen helped identify the new Ecuadorian frog species

The story centres on the Milpe robber frog, now known scientifically as Pristimantis milpe. It is not the sort of species one might expect to remain unnoticed for generations. The frog is relatively common, occupies a broad area and can be picked out at night by its call. According to the study published in Zookeys, titled ‘Long overdue: a new, widespread species of Pristimantis (Anura, Strabomantidae) from the Chocó region and the synonymy of Pristimantis subsigillatus’, its range stretches through the Chocó forests of western Ecuador and into southern Colombia, covering more than 67,000 square kilometres and extending from sea level to about 1,200 metres.For years, however, populations of this frog were assigned to Pristimantis subsigillatus. The name seemed to fit because of the way earlier specimens had been interpreted. But the classification had a weak point buried in the past: the original type specimen associated with P. subsigillatus did not actually represent the same frog as the living populations that had been given that name. The researchers’ examination showed that the historical specimen was instead the same species as P. latidiscus, a frog described four years earlier.That left the widespread Ecuadorian and Colombian populations in an awkward position. They were familiar animals in the field, but the scientific name attached to them was wrong. As Jhael Ortega, one of the study authors, put it, “such a common species has gone unnoticed under the wrong name for decades”.

How 19th-century museum specimens solved the Ecuadorian frog mystery

The decisive part of the investigation took Ron from Ecuador to England. Inside the Natural History Museum in London were the original specimens, or “types”, collected during the 19th century. These preserved animals were not simply historical curiosities. They were the reference points against which later identifications had to be judged.Ron examined the old material and compared it with frogs found in Ecuador today. The comparison exposed the problem: the historical specimens had been linked incorrectly to populations that were actually different. The museum material therefore became the missing piece in a taxonomic puzzle that had survived for more than 100 years. The researchers could then separate the old names, establish that P. subsigillatus was a junior synonym of P. latidiscus, and formally describe the previously unnamed species as Pristimantis milpe.There is something quite practical about the discovery. Nothing new had suddenly appeared in the forest. The frog had been there all along. What changed was the interpretation of evidence collected long ago. The study is a reminder that museum collections can contain unresolved scientific questions even when the specimens themselves have been sitting in storage for generations. Pensoft described the work as an example of how historical collections can be revisited to answer questions that remained open for decades.

Pristimantis milpe is a nocturnal Ecuadorian frog with a distinctive clicking call

Once the species was separated from the confusion surrounding P. subsigillatus, the researchers could give Pristimantis milpe a clearer identity. It is a nocturnal frog, and males typically call from leaves of shrubs and bromeliads several metres above the forest floor. Its call has a loud, distinctive quality that resembles a click, making the species relatively easy to detect during nighttime surveys.Its appearance also offers useful clues. Females have a noticeable colour pattern around the groin and thighs, with orange or light-blue areas marked by black spots. Males tend to have more uniform colouring. This difference between the sexes, known as sexual dimorphism, was among the characteristics considered in distinguishing the species. The frog has also been recorded in a surprisingly broad mix of surroundings, from primary forest to parks in urban areas.The distribution adds another unusual element to the story. Pristimantis milpe is associated with the Chocó region, an area recognised for its exceptional biological richness. The Ecuadorian Chocó alone is home to more than 250 amphibian species, placing the newly described frog within an exceptionally diverse community.

How a century-old taxonomic mistake kept the Ecuadorian frog hidden in plain sight

Taxonomy depends heavily on getting names and reference specimens right. When an original specimen is misinterpreted, that error can spread through later publications, museum records and field surveys. In this case, the consequences lasted for more than a century. Correcting the record required researchers to move backwards into the history of the specimens before they could properly describe what was living in Ecuador and Colombia today.The case also illustrates why a species does not have to be rare, remote or newly encountered to become a scientific discovery. Pristimantis milpe was already widespread and locally abundant. People had encountered it, researchers had collected it, and specimens had entered museum collections. Yet the animal remained scientifically obscured because the pieces of its history had not been connected correctly.In the end, the discovery depended on looking backwards. A frog in the forests of Ecuador acquired its own scientific identity because a scientist travelled to London, opened the historical record and found that an old name had been attached to the wrong animal. The specimens had been preserved for generations.